The earliest non-Indian settlers of Arizona generally came into the Gila Valley from Sonora and Sinaloa states of Mexico. During the 1840s and 1850s, prospectors from eastern United States and from Texas passed through the valley on their way to the gold fields of California. Some returned to settle. When military personnel left at the beginning of the Civil War in 1861, the territory was almost abandoned to the Indians. The Apaches remained a serious threat until 1886.

Fort Defiance, established in 1852, was the only significant white outpost north of the Gila Valley until 1863, when politicians from northern states established Prescott as the first territorial capital. Phoenix, founded by an Englishman in 1867, became the territorial capital in 1889.

Mormon settlers from Utah established communities, such as Snowflake, on the Little Colorado River of northern Arizona in the 1870s and 1880s. Mormons and others also founded new towns and cities in the Gila and Salt River valleys in the southern part of the state. Mesa was one of these southern Arizona Mormon towns.

Most cities and towns of Arizona had been founded by 1900, but some mining communities experienced new growth in the 1920s when an ethnically varied population entered the state, including Italians, Mexicans, Cornishmen, and Slavs. Today, most Arizonans identify themselves as Anglo, Mexican, Indian, Black, or Chinese. Many prominent families of southern Arizona are Mexican, and intermarriage across the border is common. A few records of ethnic groups such as Slavs and Spanish are listed in the Family History Library Catalog under ARIZONA - MINORITIES.

There was no port of entry common to settlers of Arizona. Some came through Gulf Coast ports, others through Pacific ports, still others through East Coast ports and then overland to Arizona. For detailed information on passenger lists, see the United States Research Outline.